Cost affordable carbon-phenolic ablative laminates : production and investigation of thermal-mechanical response

Ablative materials are a fundamental Thermal Protection System that allows the access to space. When exposed to high temperature, they degrade with a strongly endothermic charring reaction and by degrading they can act like thermal shield. In this thesis work, new technologies have been developed to increase the cost effectiveness and reliability of Carbon-Phenolic Ablatives. These materials are well known in literature as TPS, due to high degradation enthalpy of phenolic, but also poor interlaminar toughness of phenolics is well known. So, after a research and characterization of different resin formulation that can improve this mechanical behavior of phenolics, samples have been produced with a vacuum infusion process and they have been subjected to a oxy-acetylenic pyrolysis test to verify their capacity as thermal shield. A network of sensors, composed by thermocouples and Fiber Bragg Gratings optical fibers, has been embedded into the samples to directly record the evolution of temperature flow inside the samples. In parallel, a numerical model has been developed, that can correctly simulate the thermal behavior of these materials. This model proposes a degradation kinetics system of equations that assumes that all the thermal properties, like thermal conductivity, specific heat capacity and latent heat capacity, depends on density variation. Curves obtained with this numerical model has been compared to the experimental one.

I materiali ablativi sono un sistema di protezione termica fondamentale che consente l'accesso allo spazio. In questa tesi sono state sviluppate nuove tecnologie per aumentare l'affidabilità e diminuire il costo di carbo-fenolici ablativi. Dunque, sono stati prodotti dei provini tramite un processo di infusione a vuoto , che sono stati soggetti ad un test di pirolisi a fiamma ossi-acetilenica per verificare la loro capacità come scudi termici. Un network di sensori è stato inserito nei provini per misurare direttamente l'evoluzione della temperatura. In contemporanea è stato sviluppato un modello numerico che può simulare correttamente il comportamento termico di questi materiali.